Final: Lecture 30 Flashcards
0
Q
FA synthesis occurs primarily in the ______.
A
- Liver
- Also in brain, kidneys, and adipose tissue
- Components located in cytoplasm: Enzymes, acyl carrier proteins, co-factors, reducing power, energy (ATP)
1
Q
Major source of carbon for fatty acid synthesis is ___________.
A
•Dietary carbohydrates
2
Q
Major steps in synthesis of FA
A
- Formation of Acetyl CoA (2 carbon)
- Conversion of Acetyl CoA to Malonyl CoA (3 carbon)
- Elongation (addition of carbons)
- Desaturation (introduction of double bonds)
3
Q
________ supplies carbons for FA synthesis.
A
- Citrate
- Citrate lyase important enzyme that converts citrate–>OAA
- Malic enzyme important to convert pyruvate–>malate
4
Q
Conversion of Acetyl CoA to Malonyl CoA:
A
- Rate limiting step in FA biosynthesis**
- Catalyzed by Acetyl CoA Carboxylase (ACC)**
- Acetyl CoA converted to Malonyl CoA by carboxylation
- ACC adds a CO2 to acetyl CoA
5
Q
Regulation of ACC
A
- Allosteric regulation: citrate (+), long chain FA (-)
- Phosphorylation (-)/Dephosphorylation (+): Insulin (+), Epinephrine (-), Glucagon (-)
- Induction/repression: Gene expression up-regulated by high carb/low fat diet, down-regulated by high fat/low carb diet
6
Q
Two carbon units from malonyl CoA are sequentially added to growing fatty acyl chain to form _______.
A
•Palmitate
7
Q
The reactions of fatty acid synthesis occur on the ________.
A
•Fatty Acid Synthase Complex
8
Q
FA synthase
A
- large multi-enzyme complex
- Composed of 2 identical dimers (260 kDa each) HUGE
- Each has 7 catalytic activities and an acyl carrier protein (ACP)
- ACP segment has a phosphopantetheine (PP) residue
- Two dimers arragned head to tail conformation-PP of one is aligned with cysteinyl sulfhydryl group of another
9
Q
Reactions of FA synthesis
A
•Condensation–>Reduction–>Dehydration–>Reduction
10
Q
Regulation of FAS
A
- Allosteric effect (presence of phosphorylated sugars)
- Induction and repression at gene level
- High carb/low fat diet increases FAS synthesis
- High fat diet as well as starvation lowers FAS synthesis
11
Q
TAG packaged with apoproteins to form _______ and secreted into blood.
A
•Very Low Density Lipoproteins (VLDL)
12
Q
Eicosanoids
A
- Products generated by the oxidation of 20-carbon FA (arachidonic acid)
- Four families: prostaglandins, prostacyclins, thromoboxanes, and leukotrienes**
13
Q
Synthesis of Phospholipids (PLs) Mechanism 1
A
- Phosphatidic acid cleaved by phosphatase to form diacyglycerol (DAG)
- DAG reacts with various headgroups to form different phospholipids
- Headgroups need to be ‘activated’ prior to this reaction
- Choline headgroup combines with CTP to form CDP-Choline (activated
- Phosphocholine (PC) transferred to DAG to form phosphatidylocholine and CMP is released
14
Q
Synthesis of PLs Mechanism 2
A
- Phosphatidic acid reacts with CTP to form CDP-DAG
- CDP-DAG reacts with inositol to form PL and CMP
- CDP-DAG may react with glycerol to procuce phosphatidyl glycerol
- Forms diphosphatidyl glycerol (cardiolipin), a component of the inner mito matrix
